Positron emission tomography (PET) is a specialized radiology procedure that generates three-dimensional images of functional processes in a target organ or tissue of a body. Specifically, in PET studies, a biologically active molecule carrying a radioactive tracer is first introduced to a patient's body. The PET system then detects gamma rays emitted by the tracer and constructs a three-dimensional image of the tracer concentration within the body by analyzing the detected signals. Because the biologically active molecules used in PET studies are natural substrates of metabolism at the target organ or tissue, PET can evaluate the physiology (functionality) and anatomy (structure) of the target organ or tissue, as well as its biochemical properties. Changes in these properties of the target organ or tissue may provide information for the identification of the onset of a disease process before any anatomical changes relating to the disease become detectable by other diagnostic tests, such as computed tomography (CT) or magnetic resonance imaging (MRI).
Furthermore, the high sensitivity of PET—in the picomolar range—may allow the detection of small amounts of radio-labeled markers in vivo. PET may be used in conjunction with other diagnostic tests to realize simultaneous acquisition of both structural and functional information of the body. Examples include a PET/CT hybrid system, a PET/MR hybrid system.